"Even when a knitted garment is torn and worn, there is generally enough good yarn left in it for re-knitting into something smaller, or for combining with other wool to make another garment.
Unpick all seams carefully, avoiding cutting the loops of wool so that there will not be too many joins. Commence unravelling the garment from the cast-off edge, pulling gently to disengage the loops. As the wool is freed, wind it round a large book, pastry board, or other suitable article.
When a good amount of wool has been wound up in this way, take it carefully off the book and tie it in three or four places to make a skein.
After unpicking the whole garment in this way, wash the skeins gently in soapy water, or, if necessary, dye them. It is not always necessary to re-dye patchy wool as the uneven colour can be quite attractive when re-knitted, providing the contrast is not too violent. Now thread or tie the wet skeins on a line to dry, fastening a weight on to the bottom of them, to take out the crinkles."
Jane Foster & Margaret Murray, Modern Knitting Illustrated, Odhams Press Limited, Long Acre, London WC2, n.d. (1945 or before), p. 250